isdn: hfc_usb: Fix read buffer overflow

Check whether index is within bounds before testing the element.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/isdn/hisax/hfc_usb.c b/drivers/isdn/hisax/hfc_usb.c
index 9de54202c90c84828c86cefeeb3408b090ea0bdc..a420b64472e3229618bbd03b0edcf5c60227481d 100644 (file)
--- a/drivers/isdn/hisax/hfc_usb.c
+++ b/drivers/isdn/hisax/hfc_usb.c
@@ -817,8 +817,8 @@ collect_rx_frame(usb_fifo * fifo, __u8 * data, int len, int finish)
        }
        /* we have a complete hdlc packet */
        if (finish) {
-               if ((!fifo->skbuff->data[fifo->skbuff->len - 1])
-                   && (fifo->skbuff->len > 3)) {
+               if (fifo->skbuff->len > 3 &&
+                               !fifo->skbuff->data[fifo->skbuff->len - 1]) {
 
                        if (fifon == HFCUSB_D_RX) {
                                DBG(HFCUSB_DBG_DCHANNEL,